The invention relates to a semiconductor component having impurity atoms introduced by ion implantation and a method for making the same.
The patent U.S. Pat No. 5,322,802 discloses electrically activating impurity atoms in semiconductor components, in particular, SiC components, by annealing the radiation damage in the semiconductor caused by ion implantation of the impurity atoms in the course of a thermal annealing process at a high temperature.
Furthermore, the literature discloses that high temperatures of significantly more than 1500xc2x0 C. are necessary for activating the impurity atoms. On the one hand, the resistance of the component is intended to be small, i. e., a sufficient number of impurity atoms must be activated in the semiconductor; on the other hand, microscopic examinations show that the near-surface regions of the semiconductor, which are disturbed by the implantation of the impurity atoms, only recrystallize at a temperature considerably above this temperature and thus reattain a sufficiently crystalline order. This is explained, for example, in the publication by J. R. Flemish, K. Xie, H. Du, S. P. Withrow, Journal of the Electrochemical Society, vol. 142, No. 9 September 1995, p. L144-L146.
While improved electrical properties are observed after the annealing process at a high temperature, there is a marked deterioration of the surface morphology of the semiconductor. But in order to produce highly integrated components, the surfaces must be as smooth as possible. To accomplish this objective, expensive and time-consuming polishing processes are required after the annealing process.
It is the object of the invention to propose a component and a method for its fabrication, wherein the annealing process is permitted at temperatures above 1500xc2x0 C., while the surface roughness of the component deteriorates by no more than 15 nm compared to the initial value and the electrical activation is improved.
This object is accomplished by a method for making a semiconductor component including the following steps subsequent to the ion implantation process carrying out an intermediate temperature treatment as a conditioning step at temperatures between 500xc2x0 C. and 1500xc2x0 C. for a limited time duration and subsequently carrying out the annealing process at temperatures above 1500xc2x0 C.
This object is further achieved by a semiconductor component having impurity atoms introduced in near-surface regions by ion implantation, where the impurity atoms are electrically activated by a thermal annealing process and the component has a mean roughness value of less than 15 nm immediately after the annealing process.
Modifying and advantageous features can be taken from the dependent claims and from the description.
According to the invention, a component is subjected to an annealing process comprising a first step in which the near-surface regions of the semiconductor are conditioned, followed by a second step in which the implanted impurity atoms in the semiconductor are electrically activated.
Immediately following the annealing process and without further measures, the component according to the invention has a low mean surface roughness as well as a large number of electrically activated impurity atoms. It is particularly advantageous that, after the annealing process, the surface morphology is hardly changed compared to the initial state in spite of the effect of high temperatures. Measures such as expensive polishing processes can be omitted which, in an industrial production process, are time-consuming and cost-intensive.
It proves to be advantageous that such smooth surfaces are particularly suitable for being connected through a solderless and adhesive-free bonding process wherein the linkage comes about through the action of quantum electrodynamic effects between the atoms of the two surfaces to be bonded.
In the first step of the annealing process, the near-surface regions of the component are conditioned and stabilized vis-a-vis the further process steps. Therefore, high temperatures can be applied in a subsequent process step for the optimum electrical activation of impurity atoms, with the temperatures being comparable to temperatures that are generally used for annealing processes. A two-stage process with two successive temperature steps is advantageous while the temperature level is rising. But, advantageously, the transition from conditioning to activation can also take place by means of one or several temperature ramps within the process or also through temperature profiles combining temperature plateaus and temperature ramps.
It is particularly useful to initiate the conditioning already during the ion implantation if the latter is carried out at an elevated temperature.
The method according to the invention is suitable for all semiconductors. Preferably, it is used for those which tend to suffer a loss of material at elevated temperatures, e. g., through sublimation of a component of a semiconductor material.